The present invention relates generally to signal distortion monitoring and more particularly to the distortion of the pulse signals representing coded groups of information. Coded groups of pulses presently are widely used such as in digital computers, data processing, radar and telegraphy. When mark and space codes are employed as in telegraphy, the information transmitted is represented by a series of ideally rectangular pulses. The leading and trailing edges of these pulses are the transitions from mark to space or space to mark. Although ideally the transitions are abrupt, in practice they become distorted for various reasons such as ionospheric path reflections.
Heretofore many attempts have been made using signal combining techniques, analog time base measurements and cathode ray tube display techniques to give indications of the distortion of the pulses on the line. The U. S. Navy has in the past used a distortion analyzer which functions by looking for the position of the leading or trailing edge of the mark or space pulse to determine if it occurred too early or too late and then averages the effect over a number of pulses. Historically, the distortion analyzer meter output did not correlate with the printer output at the receiver end of the system. A simplistic explanation of this non-correlation is that the crypto device, intermediate the receiver and the output printer, utilizes the data pulse midpoint as a basis of data recognition whereby the trailing or leading edge location is usually an irrevelant consideration. Other distortion monitoring techniques have had only a limited degree of accuracy.